During the last several years a great deal of attention has been paid to composite materials. Composite formulation is a prime method of improving the matrix polymer's rheological properties. In particular, recent work has focused on using liquid crystal (LC) polymers as the reinforcing component in the composite. Thus, the preparation of blends of various LC polymer systems and semi-flexible thermoplastics has been attempted in the hope that the LC material will reinforce the thermoplastic on a molecular or supramolecular level. Molecular composites based on LC polymers would have several advantages over conventional macroscopic composites including: lower melt viscosities; increased homogeneity between phases; and less mechanical wear on processing equipment.
Two means for obtaining a LC molecular composite can be visualized. The first method involves simple blending of the LC component into the flexible matrix polymer. The second method deals with preparing copolymers comprised of rigid rod and flexible components, both by solution or by melt polymerization techniques. For example, Japanese Pat. Publ. No. 63/317,524 teaches formation of copolyesters by reacting an aliphatic diol with an aromatic dicarboxylic acid and an aromatic oxy acid.
A series of thermotropic LC polyesters comprising a rigid aromatic triad unit and a flexible methylene spacer were developed by Lenz et al., and are described in Polymer J., Vol. 14, p. 9 (1982). These materials have the repeat unit ##STR1## where Ar is a phenyl ring and n is an integer of from 2-10, such as 4. The phenyl ring substituents are para. These materials are considered to be triad aromatic ester mesogenic units comprising a flexible polyalkylene spacer in the main chain thereof.
Recently, Shin et al. in Polym. Eng. Sci., Vol. 30 pp. 13-21 and 22-29 (1990) have explored blends of such a triad type polymer, containing a decamethylene spacer, with poly(ethylene terephthalate) (PET) and nylon 66, respectively. The results indicated an improvement in the strength and modulus of the matrix polymer. Good adhesion was also seen between the LC/matrix polymer phases.